The present invention relates generally to engine throttle controls, and more particularly, to a nonadjustable throttle linkage connecting a throttle assembly to a throttle input.
During operation of most internal combustion engines, an operator increases the operating speed of the engine by increasing a throttle actuator. In highway vehicles, the throttle actuator is commonly referred to as a gas pedal or, in motorcycle-type devices, a twist hand grip accelerator. In non-highway use engine equipped devices, the accelerator is often generically referred to as the throttle or a throttle actuator. In watercraft, the throttle actuator is often located near a control station, or bridge, and is often a hand lever having linear motion that an operator adjusts in order to manipulate the operating speed of an engine in communication therewith.
The throttle actuator is often connected to a throttle linkage assembly that is connected to a throttle assembly mounted directly about an engine. The throttle assembly generally includes a throttle body having an opening therethrough, a throttle plate positioned in the opening of the throttle body, and an actuator connected to the throttle plate. Commonly, the throttle linkage connects the throttle assembly to the operator controlled throttle actuator such that movement of the throttle actuator results in a change of position of the throttle plate of the throttle assembly. As an operator desires to increase the operating speed of the engine, and the engine demands more combustion gas in response to the desired increase in engine speed, the operator advances the throttle actuator which in turn rotates the throttle plate relative to the throttle body opening.
Generally, as an engine is accelerated, the combustion process requires more fuel and more combustion air. As an operator advances the throttle actuator, the throttle plate opens, thereby allowing more combustion air to pass to the combustion chambers of the engine. The movement of the throttle plate relative to the movement of the throttle actuator is partly dependent on the throttle linkage disposed therebetween. In an effort to better control the responsiveness of the engine and allowance for tolerance, the throttle linkage disposed between the throttle assembly and the throttle actuator often includes some form of adjustment, such as independently adjustable links. In older engines, the adjustability of the links was also used to set idle speed.
The throttle linkage assembly can also be adjustable relative to a plurality of throttle stops. Such adjustment means often includes a plurality of screws that restricts the movement of individual links. Movement of the throttle links is often minimally fixed between fixed throttle stops. The throttle linkage is often adjusted relative to a first throttle stop to set an idle throttle linkage position that corresponds to an idle engine speed. Adjusting the throttle linkage relative to the first throttle stop often determines the relation of the throttle linkage to the throttle plate to ensure smooth and repeatable idle engine operation. As these older engines are operated, an operator could acoustically determine when the preferred idle orientation occurs. In much the same way, a second throttle stop is often implemented to set a wide open throttle position. Improper adjustment of the throttle linkage from the first or second throttle stops results in rough running engine idle speed, engine stall, or a fast running idle engine speed. Additionally, operating an engine at any of these conditions for extended periods of time results in inefficient use of engine fuel and detrimentally affects engine emissions.
Drawbacks to the adjustability of the throttle linkage assembly includes the adjustment means inadvertently coming loose and operator tampering. If the throttle linkage adjustment inadvertently comes loose, the engine may be operated outside a preferred range without operator knowledge. While any change in the operation of the engine with the adjusted linkage orientation may be imperceptible to the operator, fuel efficiency and engine emissions are affected. Similarly, an operator may adjust the throttle linkage outside of it's preferred operating range in a effort to improve the perceived operation of the engine. Such manipulation can result in damage to engine components not limited to the throttle assembly. Particularly in two-cycle engines where the fuel and air supplied to the engine perform cooling functions during operation, manipulation of the throttle assembly resulting in changes to the flow of combustion fluids through the engine can lead to overheating of engine components.
While many believe that two-stroke engines are generally not environmentally friendly engines, such preconceptions are misguided in light of contemporary two-stroke engines. Modern direct injected two-stroke engines and, in particular, Evinrude® outboard motors, are compliant with, not only today's emission standards, but emission standards well into the future. However, since these engines are so advanced, they require trained technicians perform certain repairs and adjustments. As such, a significant portion of the ability to adjust these motors has been eliminated or restricted to qualified personnel in an effort to ensure the future emission efficiency of the en- gines.
It would therefore be desirable to have a throttle linkage and method of manufacturing an engine with a throttle linkage where the throttle linkage has no means of adjustment.